Two common devices used to measure a child are:

1. Stadiometer:
   A stadiometer is a calibrated ruler or measuring rod used to measure a person's height. It often includes a sliding headpiece to compress the hair and ensure an accurate measurement against the vertical scale.
2. Infantometer:
   An infantometer is a specialized measuring device used to measure the length of infants and toddlers who cannot stand. It typically consists of a flat, horizontal surface with a fixed headboard and a movable footboard.